docker-compose up in terminal works, doesn't work in PhpStorm

I have been using docker-compose for a while now and recently found out that PhpStorm has docker-compose functionality. Great!

When I run the deploy command from the docker window, I get the error message "Some services/containers not started", showing an error against my "composer" container. See in the screenshot points 1 and 2.

When I run `docker-compose up` from the terminal, it works fine and my containers start.

If I comment out the composer section, PHPStorm doesn't fail. The combination of which section works vs. which section needs commenting out doesn't follow any particular pattern. See in the screenshot points 3 and 4.

If I remove the composer service from my docker-compose.yml, it deploys with no problem through PhpStorm.

Here's my docker-compose.yml: http://paste.ubuntu.com/25424218/

Here's the full output of running the deployment within PhpStorm: http://paste.ubuntu.com/25424222/

Here's the full output of running docker-compose up in the terminal: http://paste.ubuntu.com/25424225/

As you can see, composer runs its install command nice and quickly, then exits with code 0 as expected (as this is a one-off script to be ran at the start of the deployment).

It would be useful to know exactly what command is being ran with the deploy button in PhpStorm.